1. Field of the Invention
This invention relates to an exhaust muffler device, more particularly to an exhaust muffler device used with an internal combustion engine.
2. Description of the Related Art
An exhaust muffler device is generally mounted between an exhaust manifold and a tailpipe of an internal combustion engine to reduce the noise generated by the engine as a result of the sudden expansion of combustion chamber exhaust gases. As disclosed in U.S. Pat. Nos. 6,089,347, 7,798,286 B2, and 7,243,757 B2, conventional mufflers are generally classified from the structural consideration as two basic types: a compartmentalized type which comprises a plurality of sealed, noise entrapment chambers, and a straight through muffler which comprises a perforated duct within a sealed housing. The compartmentalized type of muffler uses various volumes of different shaped or sized chambers interconnected with pipes and can dampen resonance frequency, but a relatively large volume of the chambers is required to generate resonation therein. The straight through muffler uses an offset side branch off a straight through pipe. When the sound wave reaches a closed end of the side branch, it reflects back to be dampened. However, an effect of the presence of reflector partitions and chamber walls is to produce a back pressure in the exhaust path of exhaust gas, which robs the engine of some amount of horsepower.